This invention is generally directed to toner and developer compositions, and more specifically the present invention is directed to colored toner compositions, and colored developer compositions, containing therein infrared absorbing additives, or infrared absorbing colorants. In one embodiment, the present invention is directed to colored toner particles suitable for flash fusing systems, wherein the particles contain therein infrared absorbing additive substances including various phthalocyanine compositions, and other compositions. In one variation of the present invention there is provided infrared absorbing additives for color toners, wherein the additive also functions as a charge enhancing substance. The toner and developer compositions of the present invention are especially useful for causing the development of images in electrostatic imaging systems, particularly those systems having incorporated therein a flash fusing device.
The formation and development of images on the surface of electrophotographic materials, referred to in the art as photoreceptors for example, by electrostatic means is well known, these processes involving subjecting the photoconductive material to a uniform charge, and subsequently exposing the surface thereof to a light image of the original to be reproduced. The latent image formed on the xerographic photoconductive surface is developed with toner particles specifically prepared for this purpose. Thereafter the develped image can be transferred to a final support material such as paper, and affixed thereto in order to obtain a permanent record or copy of the original. Numerous methods are known for applying the electrostatic toner particles to the electrostatic latent image, including for example, cascade development, magnetic brush development, powder cloud development, and touchdown development.
The image formed can be fixed by a number of various well known techniques including, for example, vapor fixing, heat fixing, pressure fixing, or combinations thereof, as described for example in U.S. Pat. No. 3.539,161. These techniques of fixing while suitable for certain purposes suffer from some deficiencies, thereby rendering their use either impractical or difficult for specific electrostatographic applications. For example, it is difficult to construct an entirely satisfactory heat fuser which has high efficiency, can be easily controlled, and has a desirable short warm-up time. Also, heat fusers sometimes burn or scorch the support material. Somewhat similar problems including for example, image offsetting and undesirable resolution degradation, are present with pressure fusing methods. Additionally with these processes, consistently desirable permanent images are not obtained. Vapor fixing has advantages, however, one of its main disadvantage is that a toxic solvent is used, therefore in many situations this method becomes commercially unattractive in view of health hazards associated therewith. Also, equipment and apparatus to sufficiently isolate the fuser from the surrounding area is very complex, costly, and difficult to operate.
Many of the modern electrostatographic reproducing apparatuses, which are capable of producing copies at an extremely rapid rate, created the need for the development of new materials and processing techniques. With these systems, radiant flash fusing is one of the preferred fixing processes selected in that the energy which is emitted in the form of electromagnetic waves is immediately available and requires no intervening medium for its propogation. Although an extremely rapid transfer of energy between the source and the receiving body is provided with the flash fusing process, a problem encountered with this process resides in obtaining an apparatus which can fully and efficiently utilize a preponderance of the radiant energy emitted by the source during a relatively short flash. The toner image in these systems usually comprises a relatively small percentage of the total area of the copy receiving the radiant energy, causing most of the energy generated to be wasted as it is transmitted to the image, or is reflected away from the fusing areas. Furthermore, many of the toner compositions currently available, particularly colored toner compositions, contain pigments which do not absorb energy in the near infrared region of the spectrum, thereby necessitating the supply of larger amounts of energy to these compositions in order to effect fusing. Moreover, many of the known colored toner compositions contain pigments therein which do not absorb energy in the near infrared and/or ultraviolet region of the spectrum, thus only about 33 percent of the spectral energy generated for example, from presently used Xenon lamps is undesirably absorbed by the colorants contained in the toner composition.
Generally, radiation energy emitted from a Xenon flash lamp, or similar source, is absorbed by the pigment or dye contained in the toner composition, and thereafter this energy is convered to thermal energy by a radiationless decay process enabling heat generation, causing the toner particles to fuse. The flash energy used is absorbed in a layer of toner of finite thickness adjoining the outer toner surface, with absorption being greatest at the surface. This energy also constantly decreasing with increasing distance from the outer toner surface. The flash generated is of very short duration, on the order of about one millisecond, and consequently the toner regions very close to the surface are heated to a much higher temperature than the toner mass as a whole.
Examples of known flash fusing systems that may be selected for the present invention, includes those as described in U.S. Pat. Nos. 3,529,125; 3,903,394; and 3,474,223; the disclosure of each of these patents being totally incorporated herein by reference. Generally, the flash fuser selected contains a Xenon lamp, the output of the lamp being primarly in the visible and near infrared wavelengths of the regions. The output of the flash lamp is measured by Joules using the capacitor bank energy in accordance with the formula 1/2 CV.sup.2 wherein C is capacitance and V is the voltage. One of the main advantages of such a flash fuser over other known methods of fusing is, as indicated herein, that the energy propagated in the form of electromagnetic waves is immediately available, and no intervening source is needed. Also, such flash fusing systems do not require long warm-up periods, and the energy does not have to be transferred through a relatively low conductive or corrective heat transfer mechanism.
Furthermore, many of the color developer compositions selected for use in flash fusing systems do not possess high toner fusion efficiency, and do not absorb light in both the visible and infrared region of the spectrum. Moreover, in view of the intensity of the flash radiation supplied to the toner composition, the higher temperature generated in the toner causes decomposition thereof and the undesirable volatile material that is formed cannot be absorbed or entrapped by the decomposed toner matrix. This material thus escapes from the toner layer before the toner can cool. A toner composition with high thermal stability, such as several of the color toners of the present invention, will substantially eliminate this problem. Also, the toner compositions of the present invention contain pigments which absorb energy in the infrared and ultraviolet light region of the spectrum, enabling these compositions to absorb light from infrared emitting devices including commercially available Xenon lamps. Additionally, many of the pigments used in the toner compositions of the present invention can function simultaneously as an infrared absorbing component, and a charge enhancing material.